Sesame straw was used as the precursor for the preparation of APBCs. KOH and Ca(OH)2 were used as co-activators. The weight ratio of the three was 1: 1: 1. And the mixed samples were pyrolyzed by direct pyrolysis method. The calcination temperature was 800 ℃ (heating rate = 3 °C/min), and nitrogen (N2) (flow rate = 200 mL/min) was selected as the shielding gas. BCs was prepared in the same way, but no activator was added. After calcining, the as-prepared carbon was taken out and cooled to room temperature. HCl solution (1 M) was selected to wash the samples for depriving water-soluble substances and other impurities from the as-prepared carbon. After pickling, the black carbon residue was washed using ultrapure water and passed through 0.45 µm membrane for filtration until the pH reaching 7. Finally, the treated samples were dried in a constant temperature drying oven at 85 ℃ for 48 h, then APBCs were obtained.